1. Field of the Invention
This invention relates to improvements in connection with measurements for estimating body composition, particularly of the type using near-infrared interactance. More particularly, this invention relates to a measurement locator and light shield for use with an interactance probe while conducting such measurements and a method for use thereof.
2. Description of the Prior Art and Problem Involved
The United States Department of Agriculture (USDA) has demonstrated that light absorption can measure the chemical constituents within organic products. One application of this technology was described in the technical paper "A New Approach for Estimation of Body Composition: Infrared Interactance" published in the American Journal of Clinical Nutrition, 40, Dec., 1984, pp. 1123-1130. In this paper the USDA described and demonstrated that measurement of body fat can be made by performing optical measurements on the biceps (i.e., half way between the elbow and the shoulder of the prominent arm--the prominent arm is the arm that is used for writing).
An adaptation of this technique was patented by Robert D. Rosenthal, et al. and assigned to Trebor Industries, Inc. of Gaithersburg, Maryland in U.S. Pat. No. 4,633,087 granted Dec. 30, 1986. In this Rosenthal, et al. patent a low-cost "light wand" is disclosed to make measurements similar to those mentioned in the USDA paper. The Rosenthal, et al. technique was further improved in patent application Ser. No. 058,550, filed June 5, 1987, of Rosenthal, et al. which provides and obtains an increase in precision of the measurement by adding narrow bandpass optical filters.
This type of quantitative in vivo measurement of body composition is expected to have many applications in human diagnostic functions in the next several years. However, the present state of the art leaves unsolved three fundamental problems which are required in addition to having a proper "light wand and measurement system." These additional unsolved problems include:
1. The fact that external light can "wash out" the measurement, thus the need to exclude all external light so that the measurement is not "washed out".
2. The necessity for taking the measurement at precisely the same point on the body of the individual being measured each time the measurement is made so that a proper comparative measurement can be obtained.
3. The need for a second person to perform the required measurement and the test on the individual, i.e., the need for an outside operator detracts from the versatility of the prior art.
All three of the above-mentioned problems are solved with the simple device and method of this invention.
The previous approach to using such instruments was to use another person (i.e., an operator) to measure the length of the arm between the shoulder and the inside of the elbow of the person undergoing the test (test person). The operator would then mark the location on the arm of the test person and then place the flexible light probe at the properly located marked point. A small flexible optically opaque light shield affixed around the probe would attempt to protect the measurement from ambient light. Although this previous approach worked fairly well, it had the following limitations:
1. It required an outside person (the operator) to measure the length of the arm each time the tested person is to be tested. This slows down the measurement process and leads to possible errors in the location of the measurement.
2. Depending on how well the light seal gasket is used, external light may or may not interfere. An individual's arm, by its very nature, is quite transparent to light in the near infrared spectrum, thus if the measurements are taken in sunlight or in other broad spectrum light, the arm must be totally enclosed which causes a further problem for the outside operator.
3. The use of a second person or outside operator is required in order to accomplish the test, thus the test cannot be self-administered.